On 8/11/05, Phil Kulak <[EMAIL PROTECTED]> wrote:
> I didn't get much input on this when I was commenting in another's
> thread, so I thought I'd start a whole topic on it. Anyway, is it
> planned to give the developer some way to get at thrown exceptions in
> a central place and handle them? I keep coming on situations when I
> need to do this, and I have no idea how to go about it.
>
> Some examples. You've got a shopping cart and a checkout process. You
> don't want the user to be able to start the checkout process with an
> empty cart. My first instinct is to check for an empty cart on
> construction and throw a custom exception if the cart's empty, but
> since I can't get to it further up the stack, that doesn't get me
> anywhere.
I don't see how this is different from validating a form. How exactly
a user would get to checkout? Either with button or link. Link should
not be a page link, it should be what JSF calls "command link".
Basically, it is the same submit action on a page, but via link. Ok,
it is not a submit, but it still should call event handler on a
current page. So, you can check for empty cart, generate error message
and redirect to same page.
> Or how about if I user tries to view a bookmarked page for an object
> that doesn't exist anymore? You can't draw the page without an object
> to draw from, so you throw an exception. It would be nice to then show
> the user some friendly message ("the object doesn't exist
> anymore..."), but currently your only options are a stack trace or a
> general exception message.
"Object not found" is a pretty specific exception. There should be a
app-scoped page for this. Also, each Page can define "not found"
location for itself.
Why you cannot get exception further up the stack? How about global
error handler for a start, like Struts has? Where you can define all
exceptions you want to catch globally.
Michael.
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